1. Field of the Invention
The present invention relates to an information storing disk apparatus and more particularly, a magnetic or optical disk apparatus intended to use a flexible information storing disk.
2. Description of the Related Art
It has been asked these days that the magnetic disk apparatus can achieve mass storage and high speed access and be smaller-sized with lighter weight and lower cost.
The hard disk apparatus is well-known as being characteristic of mass storage and high speed access. In the case of this hard disk apparatus, however, the inertia of its hard disk medium is quite large. The spindle motor for rotating this hard disk medium becomes therefore extremely large in size and its rising time is long accordingly. Further, the hard disk apparatus usually uses floating head sliders and the hard disk medium is rigid. If magnetic heads of the head sliders strike against the hard disk medium, therefore, impact applied to the magnetic heads is quite large. In addition, the hard disk medium is comparatively high in its manufacturing cost.
Although the hard disk apparatus is characteristic of its mass storage and high speed access, it was difficult to make the device small in size and low in cost.
On the other hand, the floppy disk apparatus is well known as being small in size, light in weight and low in cost. It has been variously tried that the flexible magnetic disk for the floppy disk apparatus is rotated at high speed to achieve mass storage and high speed access as well as to make the device small in size and low in cost. However, the floppy disk apparatus is intended to read and write signals on and from the disk, keeping the magnetic head contacted with the flexible disk. When the flexible disk is rotated at high speed, therefore, the disk is remarkably damaged and the wearing of the disk is quite notable.
It was therefore difficult for the floppy disk apparatus to achieve mass storage and high speed access as well as to be made small in size, light in weight and low in cost.
In the case of the floppy disk apparatus intended to use the flexible disk, the position of the magnetic head relative to the disk must be accurately held to achieve mass storage and the like. The flexible disk can seemingly keep its flatness due to centrifugal force at the time of its high speed rotation. This enables the position of the magnetic head to be almost accurately kept relative to the disk. However, it is not assured that the flexible disk can always keep its flatness not to vibrate at the time of its high speed rotation.
This asked the following means to be conventionally employed to prevent the vibration of the disk. As disclosed in U.S. Pat. No. 4,419,704 and others, only one fixed Bernoulli is arranged to face the one surface of the disk with an extremely small clearance (or 100 .mu.m, for example) interposed between the plate and the disk. Very little air flow is thus created between the Bernoulli plate and the disk at the time when the disk is rotated at high speed, so that this air flow can support the disk with a certain pressure to prevent the vibration of the disk. However, the disk contacts the Bernoulli plate at the time of its speed rotation. This causes the disk to be damaged and remarkably worn by the Bernoulli plate at the time when the disk is started and stopped.
U.S. Pat. No. 4,661,875 and others disclose another Bernoulli plate separated from the disk by an extremely small distance (or 100 .mu.m, for example) and rotated together with the disk. In this case, too, the centrifugal force makes it possible to create very little air flow between the Bernoulli plate and the disk and in the radial direction of the disk to prevent the vibration of the disk. However, the disk rotates together with the Bernoulli plate and the inertia of the rotating matters becomes large. This makes it impossible to make the disk apparatus small in size. In addition, head access to both sides of the disk is left impossible, thereby causing mass storage not to be achieved.
Various kinds of means have been employed to prevent the disk from being vibrated, but they usually followed such drawbacks that the disk was worn, that the inertia of the rotating matters was large and that mass storage could not be achieved.